In this paper, a study has been made of proton implantation and annealing behavior of GaAs. The single crystal wafers used in the implantation were oriented typically at 1-3° away from (100), and doped with Sn to 5×1017-1×1018cm-3. The implantation was carried out at room temperature in a proton accelerator and ion implantation machine with an energy of 8×104-2×106eV. Following bombardment, the implanted area was delineated by means of an A-B etchant, and the penetration depth of proton xj was determined. The xj values obtained can be related to the implantation energy E as follows xj= (8.716×10-4+4E-1)E1.365,where Xj is in ?, E in eV. The maximum lateral spread of the proton XL as a function of energy was also, determined, and found to be ～104? when E>3×105eV. The proton implanted samples were annealed at 150-800℃ for 5 min. A X-ray double crystal difractrometer was used to characterize the recovery of strain, and a electrometer was used to determine the resistance variation with annealing temperature. The results showed that the critical dose φ* for amorphous layer formation after proton implantation was ～1016cm-2, and the recovery of strain began at 150°, and virtually stopped at 450°. In the temperature range 150-450°, there were no significant variation in implanted resistance. The recovery of resistance oecurred only at higher temperatures. The project range of proton Rp, the electron stopping power Se(E), the nuclear stopping power Sn(E), and the mechanism of annealing of implanted proton in GaAs are discussed on the basis of the present experimental results.